EE Idea Bank

Appliance Efficiency

• A compact fluorescent bulb is more expensive to purchase than an incandescent bulb, but much less expensive to operate. Sometimes the extra expense is worth it in the long run, since an 18-watt fluorescent bulb gives as much light as a 75 watt incandescent bulb. Complete this chart to determine which is a better buy.

Type of Bulb	Cost to Buy	Power Rating	Ave. Life	Electr. Energy Req’d	Price of Electr.	Cost of Electr.	Total Cost	Total Cost per hour of use
Incandescent	$0.41	90 Watts	750 hours		$0.14/kWh
Compact fluorescent	$9.95	20 Watts	7500 hours		$0.14/kWh

*The better buy is...

• Suppose you could choose between the two refrigerators at the extremes of energy efficiency: one uses 742 kWh/year and the second uses 836 kWh/year. How much could you save in your electricity bill over a ten-year life of the refrigerator by choosing the more efficient model? Show your work!

1. Make a list of five appliances in your house. Write the names of each in the Appliance Device column.
2. Put the appliance's power rating in the second column. You must change all values to kW. If values are given in watts, divide by 1,000 to get kW.
3. Give a rough estimate of usage time in the Hours-Per-Day column. For intermittent appliances, estimate how much time it would actually be running during a day and add 0.5 hr
4. Calculate the daily kilowatt-hours, or kWh. Multiply the power rating (in kW) by the usage time (in hours per day).
5. Calculate the cost per day for each appliance using your own local cost of electrical energy in cents-per-kWh ($0.15/kWh). Multiply the kilowatt-hours (kWh) by the price (in dollars). Then calculate the total electric cost for one day, and for one month.

Appliance Power (Watts)	Power (kW)	Est. Daily Use (hrs)	Daily Cost ($)	Monthly Cost ($)

Project 1. Maria's Market: Please complete the table.

Appliance	Watt Rating (watts)	Time Used (per day)	Watt-hours Needed
Lights	15 W	4 h
Refrigerator	120 W	9 h
Blender	75 W	40 min

Total watt-hours needed:

To: Consultants
From: Beth Richards
Subject: Batteries

The batteries we have been using in Central America to store energy from our solar panels are not perfect. In some cases we can get out only 60% of the energy that we store in them. The remaining energy is converted into heat energy, not electrical energy. Help me determine how this will affect our project for Maria’s Market.

If we supply batteries that store 200 Watt-hours, with a 75% efficiency rate, determine the total number of batteries Maria will need to capture into her batteries to supply the total watt-hours you calculated.

Assignment:
Use the Electrical Circuits simulation at
http://phet.colorado.edu/new/simulations/sims.php?sim=Circuit_Construction_Kit_ACDC

Tasks:
1) Find a way to light a bulb with 1 light bulb, 1 battery, and 2 wires. Move it to the side of the workspace.
2) Find a way to light a bulb with 1 light bulb, 1 battery, and 1 wire.
3) Choose the visual called "Schematic". Make a screen shot with the circuits in Schematic and Lifelike visuals.